Commuting costs Americans money, time, health and sanity. Workers spend about 50 minutes a day on average getting back and forth to the office, but that number hides huge differences, with some 1.7 million Americans spending more than three hours a day commuting, and another 2.2 million Americans traveling at least 100 miles a day. (About 600,000 people — the megacommuters — are forced to do both.) And then there’s the traffic — in 2011 commuters spent on average 38 hours stuck in gridlock, some four hours longer than the average workweek. Commuting costs Americans about $1,500 a year on average, and that doesn’t include the $818 in productivity that the average American loses because of the hours wasted in traffic. Oh, and researchers have found evidence that long commutes are linked to obesity, neck pain, insomnia and divorce.

So you’d think that Congress would want to take steps to ease the pain of commuting, perhaps by diverting drivers to public transit, which alleviates traffic and helps the environment. Through this year, Americans have been able to set aside up to $245 a month in pretax money for use on public transit. (That includes commuter rail, subways, buses, trolleys and ferries — basically anything you’re not driving yourself.) But starting on Jan. 1 — thanks to Congress’s failure to renew the credit before heading home for the Christmas break — that tax break will be cut by more than 45%, and commuters will only be able to set aside a maximum of $130 a month. That could cost the heaviest users more than $1,000 a year. And to add insult to injury, the tax credit for driving commuters will actually be going up, with Americans allowed to set aside up to $250 a month in pretax money for spending on parking, an increase of $5 a month.

This is stupid. There’s an enormous public benefit to supporting public transit. The overall effect of having buses and subways available saves an estimated 4.2 billion gallons of gasoline annually, and reduces carbon emissions by 37 million metric tons a year. Tax benefits for public transit are also progressive — the median household income for the average public-transit user was $39,000 in 2007, compared with $44,389 for the population as a whole. Cutting the public-transit tax credit while increasing the credit for parking isn’t just bad for the climate — it’s patently unfair.

But let’s say you don’t use public transit (and since 80% of commuters drive alone to work, you probably don’t). Why should your tax money go to the 5% of Americans who need to use a bus or a train to get to work? For one thing, driving in America is deeply subsidized — and often by people who aren’t drivers. According to a study by the Tax Foundation, just 32% of the funding for America’s roads comes from gas taxes, tolls or other fees levied on drivers. The rest comes from the general tax fund — which includes taxes paid by people who don’t drive. (By the way, that federal gas tax — which costs 18.4¢ per gallon of gas — hasn’t increased since 1993, which threatens to leave America’s highways badly underfunded.) Compare that with the much maligned Amtrak, which covers 85% of its operating costs with ticket revenue.

The fact that we’re increasing the commuter benefit for parking while cutting it for transit is even crazier, since parking gets all sorts of invisible subsidies, like city regulations that require developers to provide parking spaces when building new housing. “Free” parking on residential streets — common even in cities as congested as New York — actually exacts a huge cost on society in gasoline burned and pollution emitted. Donald Shoup, a professor of urban planning at UCLA, found that in one 15-block commercial district in Los Angeles, drivers trolling for spots were responsible for an extra 950,000 vehicle miles driver per year — equivalent to 38 trips around the earth — and an extra 738 tons of carbon dioxide. The last thing we should be doing is further subsidizing parking.

But putting all that aside, it’s still in the interests of drivers to see the public-transit tax credit kept higher. The more commuters who switch to transit, the fewer of them there are clogging the roads. A recent study looked at the effects of the 2003 strike by L.A. transit workers, and found that the average highway delay increased by 47% when transit service ceased. A 2010 study found that without public transit, travelers would have suffered an additional 785 million hours of delay. And a healthy commuter tax credit does encourage commuters to try transit, which has been on the increase around the country, with 10.5 billion trips recorded in 2012, up 1.8% from the previous year.

Letting the public-transit credit drop is in absolutely no one’s interests — and in fact, the program enjoys broad, bipartisan support on Capitol Hill. But the credit is tied up in a larger bill that contains a grab bag of other tax credits that have either expired or are set to expire, and Congress was unable to act before the Christmas recess. An attempt by New York Senator Charles Schumer to restore the full transit credit in a separate bill — the Commuter Benefits Equity Act — failed as well. Congress will likely try to restore the credit in the new year, but even if that’s successful, trying to calculate the retroactive savings will be a headache. But as members of Congress sit in traffic — the Washington area has the worst congestion in the country — at least they’ll have plenty of time to think about it.